Treatment of clay



. No Drawing.

Patented July 29, 1 930.,

i UNITED "s'rATes A ENT OFFICE.

WILLIAM H. ALTON, NEW YORK, N. Y., ASSIGNOR T0 T. VANiD'ERBILT COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OENEW YORK which theyare combined is found in the form of small quartz particles together withfiakes of mica, both of which have to be removed be fore-the clay can be used in the manufacture.

. of paper, etc., .because, no matter how finely product as a shin ng s the grit may be ground by machinery, into the body of the clay,'the quartz always re-.

mains as a microscopic. grit to weaken the fabric, and the mica shows in .the finished 'e'ck or is liable to drop out of the paper or a 1m, leaving tiny holes.

The method commonly employedheretofore for treating clay to-separate grit fromit has been that of agitating the clay in the presence of enough'Water-to soften it to a point where it will disintegrate, using usually around nine times as much water as clay. After the clay. has beensoftened so as to set free the particles of grit to which they have-been adhering, the thin slurryofclay is passed throu h a series of troughs with cleats across the ttom or pocketsicalled rifiles in'which the particles of grit are caught, due totheir greater specifi'c gravity, while" the clay itself goes over the rifiies and is collected in vats or tanks and allowed to settle. The Water is thensiphoned off, leaving a layer of clay mud which requires several days or even weeks to suflici'ently evaporate for handling in a dry house where it is further dried and then packaged for delivery to the consumer. lVhile this Wei method of washing clay'to free it from grit is adequate, it is-wasteful and expensive, and requires the drying out of a large amount of water With artificial heat.

According to the present invention, the clay with its fine grit'particles in it is treated a in a dry way Without the necessity'of using a large amount of-water, and of removing the added Water from the clay.- a According to the present nvention, the large lumps of clay mined from the claybed TREATMENT or CLAY I I j A "Application filed August 22, 1928. Serial No. 301,433.

are first allowed to air dry for several days in a dry shed. These lumps are then subjected to a preliminary rough crushing or grinding to reduce them to a size varylng from pellets of around one-quarter inch di an'icter down' to powder, This can be accomplishedby passing the lumps through an appropriate type of crushing device, such as the Arnold Creger heavy dutyclay crusher.

The resulting mixture of fine clay and pellets of up tonne-quarter inch diameter is then passed through a rotary drier or other form of drying device to reduce the moisture content down to less than 3%. The clay thus dried contains alarge'part of the clay in the form of fine particles which can be directly separated from the-clay-by. a elective air separation treatment such as that set forth in my companion application, Serial No.

295,125. Inv such .case, uhowever, the clay which is not in a finely divided staterequires further crushing to separate the clay from the grit.

' According to thepresent invention, subject the preliminarily crushed and dried clay to a further treatment such as an impacting 'or rubbingtreatment to separate the clay adherin r to the grit. This further impacting or rubbing treatment can be carried out in suitable apparatus such as a cage 'millor dis- I integrator, or a tube mill loadedwith pebbles large'enough to rub the clay pellets to powder when rolling over and over each other,

but too small and light to crush the intermixed silica or grit particles which are set free from adhering clay and are kept intact for later separation. A cage mill is composed ofa series'o'f concentric, circular cages comprising circular rows of rods suitably spaced and parallel to the axisof rotation. -Alternate cages rotate in opposite-directions and at high velocity.' The'material which is to be I disintegrated is fediinto the center and is driven toward the outside shell by centrifu gal force. However, its passage fromthe center to the outside it is buffeted first in one I directon and then in the other by the bars of alternating cages. This bufieting knocks off from the pellets fine particles of clay but into pellets. diately adjacent to a partlcle of grit 1s denser is not sufficient to break down the particles of grit.

It will be appreciated that the grit admixed with the clay is itself in a finely divided state. In one sample, for example, the

isolated grit was of such a fineness that -prac-- tically all of it passed through #110 mesh screen and around 80% of it passed through a 60 mesh screen, while none of it passed through a 325 mesh screen, When the clay is subjected to a preliminary disintegration, the grit-bearing clay is' largely separated Apparently the clay immeor more adherent than other clay. In any event, the preliminary crushmg of the clay sets free a large part of the clay in pract cally its ultimate state of subdivision or in.

with grit particles.

In the present process, this preliminary rough crushing which sets free a large part of the clay in a sufiiciently finely divided form and leaves a considerable part of 1t,

' amounting in some cases to as much as half or more, in the form of grit-bearing pellets, is subjected after drying to a further disintegration which will set free a large part of the clay from the grit-bearing pellets, leaving the heavier grit-bearing pellets themselves 1n an uncrushed and undisintegrated condition.

The entire body of clay is then subjected to a selective air separation treatment,

The air separation treatment which is employed in the process of the present invention is one'which can be carried out rapidly and continuously with a large through-put of clay handled and of fine clay produced; I accomplish this selective air separation by using selective currents of air in separators such as the Gayco type or the Sturtevant selecti-ve type of separator. The Gayco separator is a dry centrifugal separator with air currents which enable a large through-put of clay to be handled in them and to accomplislr a selective separation of the fine clayparticles from the heavier grit particles.

This single air separation treatment enables around 80%, more or-less, of clay to' 1. The method of treating clay,

be directly obtained in a'finely divided and substantially grit-free condition .which is directly marketable as commercial clay, commercially free-from silica or other objectionable gritty matter.

After thisseparation there will remain a varying amount, for example, around 20%, more or less, of grit-bearin clay which contains substantially. all of t e grit particlestogether with the cla separated by the .se ective air separation treatment. This residue I subject to a furconditlon from the gritty residue.

grit particles.

residue which is not fine clay forexample, in a Raymond mill or in other suitable mills. The product will contain a large amount of grit reduced to an impalpable-powder. Such finely divided mixture of grit and clay can be used, for example, for

- certain paints where a rough finish is desired.

The present process can be carried out in a continuous manner, with continuous crushlng of the air dried clay, contmuous drylng of the crushed clay in a rotary or other drier,

continuous further crushing of the resulting dried clay and continuous feeding of the clay to the selective air separator and continuous selective separation of the fine clay in a substantially grit-free condition from the gritty residue. The selective air separation treatment comprises gentle air flotation andis distinguished from an air blast separation and is of a selective character such as is accomplished in separators of the typeabove mentioned, e. g., the Gayco dry centrifugal separator or the Sturtevant selective type of separator.

It will thus be seen that the present process is one of marked simplicity, and one in which a single selective air separation treatment is relied upon to separate mostof the clay in a finely divided and, substantially grit-free It will further be seen that the process is one in which there is a two-stage crushing, in the first stage of which the air dried clay is crushed to set free a large art of the. clay in the form of finely dividerl'clay together with a large part ofthe clay in the fdrm of grit-bearing pellets, and in the second stage of which the gritbearing pellets are themselves further broken down to set free the adhering clay from the Both of these crushing operations recede the selective air separation, and the rying of the clay is combined to insure that the clay when finally crushed in a regulated manner is then directly separable into fine clay and a gritty residue, with the greater part of the clay thus directly recovered in a substantially grit-free condition I claim;:

which comprises subjecting clay comprising grit of substantially imperceptiblefineness to successive regulated disintegrating operations,'with drying of the clay to give a dried and pulverized'clay containing .the individual grit particles substantially unbroken condition and containing practically all-of the clay physically separated from the fine grit particles, and subjecting such clay to recover the particles substantially free of such fine grit. a Y '1 2. The further improvement in the process flotation to separate the clay from the fine grit of claiml in which the gritty residue from and recovering the fine clay particles substanwliich the finely divided and substantially tially free of such fine grit. grit-free clay is separated, is subjected to a In testimony whereof I afiix my signature. further grinding operation to grind the grit WILLIAM H. ALTON. 7O into fine particles and to give a finegrit-bearing clay product. l

The process according to claim 1 in which a two-stage regulated crushing opera- 1 tion is'employed and in which the first stage I 75 is preceded'by air dryingv and the second stage by a further drying to give a dried product of a low moisture content. i

4. The method of treating clay, which comprises subjecting clay comprising grit of substantially imperceptible fineness in the form of lumps to air drying, subjecting the air dried clay to a regulated crushing to separate a large part of the clay in a finely divided form from grit-bearing pellets of clay, dr'yl ing the thus crushed clay subjecting the dried clayto a further disintegrating treatment to separate thegrit and clay from the grit-bean ing pellets, and subjecting the resulting dried at and disintegrated clay to gentle air flotation i my to separate directly from the grit a large part of the clay in a finely divided state and sub stantially free of the fine grit, leaving a gritbearing residue.

30 5. The method of producing an impalpable 7: i

pulverized clay substantially free from grit which comprises subjecting clay comprising grit of substantially imperceptible fineness as smined to a preliminary drying treatment and to a preliminary disintegrating treatment m whereby .to produce a dry, partial-1y disin- 'tegrated clay product, subjecting the product thusobtained to a mechanical action suflicient to separate aggregated clay particles but inp 40 sufiicient to break particles of grit and there- 195 after subjecting the material thus .disintegrated to a gentle current of air at velocity suflicient to hold in suspension a substantial proportion of the clay particles which are of '45 the desired degree of fineness but insuiiicicnt I to hold in suspension any substantial proportion of the fine grit particles associated there with,, permitting the fine grit particles to separate from the air current and thereafter i I 50 separating from the air suspension the fineclay substantially free from the fine grit. p

'6. The method as defined in claim 5, in *which'the final-disintegration treatment is efiected by repeatedly throwing the pellets containing aggregated clay particles against each other andagainst hard surfaces at a velocity adapted to cause detrition of the clay particles from. the pellets but insufficient to 0 break the grit particles.

7 The method of treating clay comprising grit of susbtantially imperceptible fineness which comprises subjecting such clay toa preliminary drying and disintegration and 65 subjecting the resultant clay to gentle air g 

